A firefighting plane drops water from Fishtrap Lake on a stubborn fire burning near the lake in Lincoln County, Sunday, July 20, 2014, near Cheney, Wash. The fire started Saturday afternoon and spread to several thousand acres, driven by high winds. (AP Photo/The Spokesman-Review, Jesse Tinsley) COEUR D’ALENE PRESS OUT

A firefighting plane drops water from Fishtrap Lake on a stubborn fire burning near the lake in Lincoln County, Sunday, July 20, 2014, near Cheney, Wash. The fire started Saturday afternoon and spread to several thousand acres, driven by high winds. (AP Photo/The Spokesman-Review, Jesse Tinsley) COEUR D’ALENE PRESS OUT

John Johnson returns to clear out and salvage remnants of his burned down home on Chiliwist Road, after the Carlton Complex fire burned through the valley, near Malott, Wash., on Sunday, July 20, 2014. (AP Photo/The Seattle Times, Marcus Yam) SEATTLE OUT; USA TODAY OUT; MAGS OUT; TELEVISION OUT; NO SALES; MANDATORY CREDIT TO BOTH THE SEATTLE TIMES AND THE PHOTOGRAPHER

Alyssa Jumors leads her horse back to her property after storing it with a neighbor, on July 20, 2014 in Carlton, Washington. Her neighbor had greener pastures, which would be safer for the horse if the wildfire got any closer to their land. The Carlton Complex fires have swept the region covering over 215,000 acres of land and destroying over 100 structures. (AP Photo/The Seattle Times, Maddie Meyer) SEATTLE OUT; USA TODAY OUT; MAGS OUT; TELEVISION OUT; NO SALES; MANDATORY CREDIT TO BOTH THE SEATTLE TIMES AND THE PHOTOGRAPHER

Washington State Governor Jay Inslee walks the perimeter of a burned down home during a visit to the residential areas on Chiliwist Road affected by the Carlton Complex wildfire, near Malott, Wash., on Sunday, July 20, 2014. (AP Photo/The Seattle Times, ) SEATTLE OUT; USA TODAY OUT; MAGS OUT; TELEVISION OUT; NO SALES; MANDATORY CREDIT TO BOTH THE SEATTLE TIMES AND THE PHOTOGRAPHER

A helicopter refills with water in the Methow River onSunday, July 20, 2014, in Carlton, Washington. The Carlton Complex fires have swept the region covering over 215,000 acres of land and destroying over 100 structures. Fire crews have been called in from all over the country in order to help contain the fire. (AP Photo/The Seattle Times, Maddie Meyer) SEATTLE OUT; USA TODAY OUT; MAGS OUT; TELEVISION OUT; NO SALES; MANDATORY CREDIT TO BOTH THE SEATTLE TIMES AND THE PHOTOGRAPHER

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OLYMPIA, Wash. (AP) â” Firefighters were making progress Tuesday in their efforts to get the largest wildfire in Washington state’s history under control, with wetter weather bringing some relief but also raising concerns about flash flooding.

The Carlton Complex of fires, which has burned nearly 400 square miles in the north-central part of the state, was 16 percent contained as of Tuesday, fire spokeswoman Jessica Payne said. A day earlier, the fire was just 2 percent contained.

Firefighters and local authorities have been heartened by forecasts that call for cooler temperatures and higher humidity. But even though wetter weather has moved in, they worry that lightning strikes could ignite more fires.

Rain also brings worries about the potential for flash flooding because so much ground vegetation has been burned away.

The National Weather Service issued a flood watch from Wednesday morning through Wednesday evening due to expected heavy rainfall.

“It takes as little as 10 minutes of heavy rain to cause flash flooding and debris flows in and below areas affected by wildfires,” the advisory says. “Rain runs off almost instantly from burned soils … causing creeks and drainages to flood at a much faster rate than normal.”

At more than 250,000 acres, the Carlton Complex is larger than the 1902 Yacolt Burn, which consumed 238,920 acres in southwestern Washington and was the state’s largest recorded forest fire, according to HistoryLink.org, an online resource of Washington state history.

The fire is being blamed for one death. Rob Koczewski, 67, died of an apparent heart attack Saturday while he and his wife were hauling water and digging fire lines near their home. Koczewski was a retired Washington State Patrol trooper and U.S. Marine.

The number of homes destroyed in the Carlton Complex fire remained at 150, Payne said. Two structures, an outbuilding and a seasonal cabin, were confirmed destroyed Tuesday in the Chiwaukum Creek Fire near Leavenworth, she said.

More than 2,100 firefighters and support crew are involved with fighting the fire, Payne said. She said firefighters have had success with fire lines on the east side of state Highway 153 between Carlton and Twisp, and they would be burning lines around Pearrygin Lake on Tuesday.

“If that’s successful, it will mitigate some of the risk to the homes in the area,” she said.

Karina Shagren, spokeswoman for the state’s Military Department, said that while the National Guard has already been offering aerial support, 100 National Guard troops were now being used on the ground for firefighting, and additional troops were receiving firefighting training for potential future use.

President Barack Obama arrived in the state for a fundraiser Tuesday, and Gov. Jay Inslee met with him in the afternoon to provide a briefing on the fires.

Inslee said he asked Obama for an emergency declaration that could provide access to resources like generators for communities without power. The declaration could also provide assistance for debris removal, Shagren said.

Inslee said officials will also assess damage to determine whether the state qualifies for a major disaster declaration that would allow people whose properties have been damaged or destroyed to seek additional resources.

“We have real significant challenges,” Inslee said. “To have the president here today is actually a stroke of luck.”

Inslee said Obama called Koczewski’s wife to express his condolences.

Also Tuesday, Patty Murray and Maria Cantwell were among a dozen U.S. senators who sent a letter to Senate leaders asking for passage of emergency legislation to allocate $615 million to fight wildfires.

Fires are currently burning in Oregon, Washington, Idaho, Utah, Arizona and California, and both Oregon and Washington have declared states of emergency.

Inslee said that while it was promising that firefighters had gained some ground on the fire, “it’s still a growing and dangerous beast.”

“We have a long, long ways to go in the fire season, months, before we’re out of the woods,” he said.